K.B.
I have been told (by hair dressers) that at infancy and around age 6 a child's hair can change... then 30ish on one might notice more changes. Sometimes you notice it and sometimes not. Also have seen it happen to many various kids with no worries, healthy kids but their hair is just changing.
If it is coming out in chunks then maybe a call to her doctors office and let them know how much is coming out at once, and how long it has been happening. Children and adults can lose chunks of hair when the body is not receiving enough nourishment (and not receiving enough nourishment can happen many different ways; food choices, how the some body processes certain foods, using that nourishment to fight other things). So if it is something that really concerns you do call her docs office BUT it morethenlikely is just that at this age her hair is changing.